1. Field of the Invention
The present invention relates generally to sleep apnea, more specifically to apparatus for alleviating sleep apnea, and still more particularly to an improved facial mask for use with respiratory assist apparatus.
2. Description of the Prior Art
It has been known for some time that sleep apnea can be alleviated through the use of respiratory assist apparatus, such as is used in the well known continuous positive airflow pressure (CPAP) therapy. It is also well recognized that one of the primary causes for patient non-compliance with CPAP or other device therapy is significant physical discomfort cause by the facial masks such devices require.
CPAP therapy essentially requires that air pressure be provided through the patient's nostrils to assist the muscles in the throat to prevent throat blockage during sleep, thus assuaging snoring and actual interruption of breathing. A respirator machine is connected to the patient's nostrils through airflow tubing connected to a facial mask placed over the patient's nose.
Because the flow of air from the machine must be directed to the nostrils with little or no loss of pressure, the facial mask is normally sealed around the entire nose and held in place by pressure from adjustable straps that fit around the patient's head. It is this necessary sealing pressure on the mask that causes the discomfort felt by the patient.
There are at least two known causes of patient discomfort when prior art apnea therapy masks are in use: pressure facial neuralgia and vacuum sinusitis. Pressure facial neuralgia is caused by tissue being compressed against the facial bones, for example by a facial mask. Vacuum sinusitis is a painful result of a build up of pressure in the maxillary cavities located in the maxillary bones located adjacent to the nose. This build up of pressure is often associated with external pressure placed on the maxillary bones by a facial mask.
One common form of facial mask used in CPAP therapy is the generally V-shaped nose mask that is placed over the entire nose, generally reaching from the bridge of the nose to just below the nostrils. Because the potential discomforts described above are well known to those of skill in the art, this nose mask is usually provided in a variety of sizes so the patient may be fitted as accurately as possible. The mask edge is provided with a soft sealing material, generally a plastic, in an attempt to fully seal air flow around the entire nose, and the mask is held in place against movement by the weight of the tubing and patient sleep motion with a set of adjustable straps that wrap around the patient's head and apply pressure to keep the mask sealed against the facial tissue.
Another form of a respiratory treatment mask is the full face mask described in an article entitled "Efficacy of a New Full Face Mask for Noninvasive Positive Pressure Ventilation," by Criner et al, CHEST, Vol. 106, pp. 1109-15, October, 1994. This TFM (total face mask) device is preferred for the NPPV therapy discussed by the authors, and is intended to reduce patients' complaints about, for example, air leakage, facial discomfort and claustrophobia. This TFM device is not suitable for most sleep apnea therapy, in particular CPAP therapy, because it is usually preferred that the mouth be uncovered.
Other forms of masks have been designed for use in apnea therapy, such as the "pillows" which comprise a pair of soft plastic tubes adapted to fit within the nostrils. This mask, though preferred over the nose mask by some patients, faces the problems of pressure caused by the connection of the air tubing to the pillow mask and the necessary holding of the tubing and mask from sufficient movement to extricate a pillow from a nostril, as well as an added problem with increased drying airflow directly within the nostrils.
Though the prior art masks have been made of a design and materials intended to ease patient discomfort, the disadvantage of causing pressure on the facial tissue and bones still exists. Some patients simply cannot accept the pain that comes with the desired therapy.